High voltage electron tube

ABSTRACT

A fully controllable electron tube comprising a plate, a cathode, a first electrode to accelerate an electron beam near the cathode and a second electrode between the first electrode and the plate, used to produce an approximately equipotential space between the first and second electrodes. The tube may be used to rectify and invert voltages in D.C. transmission lines of 1Mv and upward.

United States Patent [191 Abramian et al.

[ Mar. 19, 1974 HIGH VOLTAGE ELECTRON TUBE [76] Inventors: EvgenyAramovich Abramian, ulitsa Tereshkovoi, 15, kv. l; Vasily AlexandrovichGaponov, ulitsa Zolotodolinskaya, 9, kv. 27, both of Novosibirsk,U.S.S.R.

[22] Filed: Apr. 28,1972 [21] Appl. No.: 248,525

[52] US. Cl 3115/3, 313/6, 313/299,

313/301, 313/302 [51] Int. Cl H0lj 1/46, H0lp 29/02 [58] Field of Search313/299, 338, 6, 155, 3,

[56] References Cited UNITED STATES PATENTS 2.555350 6/1951 Glyptis313/84 Primary ExaminerRudolph V. Rolinec Assistant Examiner-Wm. H.Punter Attorney, Agent, or FirmHolman & Stern [5 7] ABSTRACT A fullycontrollable electron tube comprising a plate, a cathode, a firstelectrode to accelerate an electron beam near the cathode and a secondelectrode between the first electrode and the plate, used to produce anapproximately equipotential space between the first and secondelectrodes. The tube may be used to rectify and invert voltages in DC.transmission lines of lMv and upward.

6 Claims, 6 Drawing Figures HIGH VOLTAGE ELECTRON TUBE BACKGROUND OF THEINVENTION and capable of commutating a voltage of hundreds of kilovoltsat hundreds of amperes, wherein electrons are first accelerated toenergy close to the rated operating voltage of the tube and thendecelerated to a low energy, as a .result of which the. potentialdifference between the cathode and the plate, i.e., the voltage dropacross the tube, is not great. Thus, for example, at a rectified voltageof 2Mv the potential difference between the cathode and the plate mayamount to only a few kilovolts. In thefirst portion of the tubeelectrons are accelerated to 1 Mev and in the second portion they aredecelerated to several kev.

The length of such a tube should be rated to a double operating yoltagesince, practically, a full operating voltageis applied to both theaccelerating and decelerating sections. In this tube it is necessary toaccelerate electrons to the rated (operating) voltage which causesconsiderable thermal losses due to the accidental bombardment of tubeparts by fast electrons, local heatingup, vacuum leakage as well as aconsiderable amount of radiation. In addition, providing the electricstrength of the vacuum gap to which about a million volts is appliedwhile an electron beam of hundreds of amperes passes through the gap,poses an extremely complex physical and technological problem. Thesolution of this problem is all the more complex, the greater thevoltage, the current and the length of the operating pulse.

Q SUMMARY OF THE INVENTION- It is'a'n object of the present invention toprovide a fully controllable electron tube capable i of passing heavycurrents (hundreds of'amperes) at a small voltage across the tube thetube is also capable of withstanding inverse voltages of hundreds andthousands of kilovolts, and has smaller dimensions, a simpler designtube between the first and second electrodes to focus the electron beam.

The cathode in the electron tube may be designed in the form of a seriesof concave-faced rings placed one under the other, the first electrodein the form of a series of rings placed one under the other around thecathode and interspaced by solid annular gaps for the passage ofelectron beams, the plate in the form of a series of annular chambersequal in number to cathode rings places one under the other and havingsolid plate annular slots to receive electron beams, and the secondelectrode in the form of a series of rings placed one under the othernear the plate annular chambers and interspaced by solid annular gapscorresponding to the annular chamber slots, the cross-sections of theannular gaps between the second electrode rings being considerablylarger than those of the annular gaps between the first electrode ringsto ensure a minimal density of the electron beam near the plate.

It is also possible to design the cathode and the electron tube in theform of a series of plates along the generatrix of a cylinder, the firstelectrode in the form of a series of rods equal in number to platedplaced around the cathodeparallel to the plates and interspaced by gapsfor the passage of electron beams, the plate in the form of a series ofchambers equal in number to the plates set along a circumference largerin radius than the cylinder generatrix, each opposite its cathode plateand provided with slots to receive electron beams, the second electrodein the form of a series of rods equal in number to the chambers placednear the plate chambers and interspaced by gaps to match the chamberslots, the cross-sections of the gaps between the second electrode rodsbeing considerably larger than those of the gaps between the firstelectrode rods to ensure the minimal density of the electron beam nearthe plate.

It is desirable to provide the second electrode in the electron tubewith some means for setting up a magnetic field in its gaps forprotection against the electron beam.

An electron tube, according to the present invention, successfully copeswith the above-stated objects and may be used to rectify and invertvoltage in DC. transmission lines of l Mv and above.

In this tube the'problem of providing the electric strength of thevacuum gap long exposed to about 1 Mv and passing many hundreds ofamperes through the electron beam is obviated. Tubes, constructedaccording to the present invention, will likewise make it possible toincrease voltage and average power in the electronic and radioengineering pulse circuits.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more clearlyapparent from the following detailed description of the embodimentsthereof with reference to the accompanying drawings, in which: 4

FIG. 1a illustrates schematically an electron tube according to theinvention;

FIG. lb illustrates the distribution of potentials in this electrontube; I

FIG. 2 illustrates an electron tube with a focusing lens system;

FIG. 3a; illustrates an embodiment of the electron tube having ring-typecathodes;

FIG. 3b illustrates the lines of force of the electron tube of FIG. 3a;

FIG. 4 illustrates an embodiment of the electron tube having cathodes inthe form of plates.

DESCRIPTION OF PREFERRED INVENTIVE EWODIMENTS (FIG. 1a), a plate 2 andan electrode 3; an electrode 4 is placed between the electrodes 3 andthe plate 2.

The cathode l, the plate 2 and both electrodes 3 and 4 are enclosed in avacuum envelope 5. An approximately equal potential positive relative tothat of the cathode 1 is set on the electrodes 3 and 4. Within a space 6between the electrodes 3 and 4, the electricfield gradient set by theseelectrodes, is approximately zero. The electron flow accelerates betweenthe cathode l and the electrode 3 and then moves by inertia through thespace 6 up to the electrode 4. The potential of the plate 2 ismaintained approximately equal to that of the cathode l and, as aresult, there is a decelerating electric field between the electrode 4and the plate 2 wherein electrons are decelerated imparting theirkinetic energy to the electric field. As electrons reach the plate 2,their energy is close to zero and therefore the thermal losses acrossthe plate 2 are small. An approximate potential distribution in theabove-described conditions (conduction) is shown by the line 7 in FIG.1b. The dotted line shows the potential inside the electron beam withdue allowance for the space charge of the beam itself.

When a full operating voltage is applied to the tube (the tube is cuttoff), the potential distribution is approximately uniform (the line 8),which is achieved by usual technical facilities (sectionalization of thevacuum envelope 5, setting a voltage divider along the tube, etc.).

When the tube is conducting the potential difference between the cathode1 and the electrode 3 is much smaller than the voltage commutated by thetube. For

instance, when the operating (commutated) voltage in 1 Mv the potentialdifference may be between 10 and 50 kv and the maximum electron energyin the tube is likewise between 10 and 50 kev. As electrons reach theplate 2, their energy may be reduced to 0.3-4 kev by deceleration in thesection between the electrode 4 and the plate 2.

As the electron beam travels through the equipotential space 6, its ownspace charge will increase in size and will either be held by focusinglenses in a column of a nearly permanent diameter or provides forsufficiently large inlets in the electrode 4 and the plate 2.

FIG. 2 illustrates an embodiment of the tube wherein a magnetic focusingsystem 9 is installed between the electrodes 3 and 4. Between theelectrodes 3 and 4 the envelope 5 is sectionalized and provided with anumber of intermediate plates 10 holding lenses ll of the magneticfocusing system 9. The lenses 11 may be annular permanent magnets set inan antiparallel fashion as illustrated in FIG. 2.

The existing magnetic materials make it possible to obtain fields of theorder of 1,000 gauss with a magnet centre hole of several centimetres indiameter, The use of such magnets makes it possible to convey a beam ofabout 50 kev at 30-50 amperes in a column 1-2 cm in diameter.

Quadrupole lenses may also be used to improve the focus properties ofthe system 9.

In this embodiment the electron tube is also provided with with anadditional electrode 12 placed between the cathode l and the electrode 3and used to facilitate control over the tube current.

The plates 10 receive a potential approximately equal to that of theelectrodes 3 and 4. To maintain said potential across the plates 10 theyare interconnected and connected to the electrodes 3 and 4 via ohmicresistors 13 outside the envelope 5.

The lower is the level of electrons hitting the elements of the magneticfocusing system 9 the higher may be the resistance of these resistors13. The same resistors provide a uniform distribution of the inversevoltage across the tube.

The distance between the electrodes 3 and 4 is fully determined by thevoltage commutated by the tube and, in general, may reach a few metres.Such dimensions may be required if the tube operates at 1 Mv and theambient working medium is the ordinary atmosphere. In this case the tubelength is determined by the electric strength of the envelope face 5. Ifthe tube is placed in a better insulating medium (oil or compressed gas)it will be determined by the electric strength of the envelope surface 5facing the vacuum with possible gradients of l-2 Mv/m.

To reduce the bombardment the elements of the focusing system 9 byelectrons, the beam is shaped in the zone of the cathode l for whichpurpose, for instance, a bunched-beam gun may be used. A drop in theinverse current from the plate 2 arising out of a secondary emission, isachieved by shaping its geometry in the form of a deep cavity (chamber)or by other methods. In any event, when electrons hit the plate theenergy cannot be zero due to the thermal diversity of electronvelocities in the beam, transverse velosities as a result of lensaberrations, etc. This causes the cathode potential to be alwayssomewhat higher than the plate potential. In designing the hereindisclosed tube the minimal plate potential and, consequently, minimallosses in the tube are ensured by selecting the geometry of the plateand the electrode 4. The tube current may be increased, among otherthings, by placing within the same envelope several independent channelseach with its own cathode focusing system and plate.

FIG. 3a illustrates an embodiment of the electron tube in which thecathode 1 is designed in the form of a series of rings 14 placed oneunder the other, the electrode 3 is designed in the form of a series ofrings 15 equal in number to the cathode rings 14 and concentric relativeto them. The rings 15 are affized to one another with the aid of parts16, embracing the cathode rings 14 on the inside thus making it possibleto interspace the rings 15 by solid annular gaps 17 for the passage ofdisk-shaped electron beams without losses. Each cathode ring 14 issurrounded by a plate 2 annular chamber 18, set concentrically to thecathode ring and provided with an annular slot 19 to receive theelectron beam. The diameter of the annular chamber 18 is considerablylarger than that of the ring 14. The electrode 4 is also designed as aseries of rings 20, concentric to .the annular chambers 18 and somewhatsmaller in diameter than the chamber 18. Rings 20 are interspaced bysolid annular gaps 21 to match the annular slots 19.

The cross-sections of annular gaps 21 is five to 50 times as large asthat of the annular gaps 17. The entire above-described annularconstruction is enclosed in the vacuum envelope 5, provided with aninsulator bushing 22.

The rings 14 of the cathode l have a concave emitting (external) surfacewhich enables the size of the electron beam at first to be reduced alongthe tube axis 23. The electrons accelerated in the section between thecathode l and the electrode 3 are then propelled in the approximatelyequipotential space 6 towards the electrode 4. Meanwhile, thecross-section of the beam considerably increases and the density fallsoff accordingly. The low density of the beam in the section between theelectrode 4 and the plate 2 (the deceleration zone) facilitates thedeceleration of electrons to low energies.

To protect the electrode 4 against undecelerated electrons a magneticfield may be set up in the gaps 21, somewhat reducing the size of thebeam in the zone of the electrode 4.

Such a magnetic field may be set up by passing electric current throughthe rings from a source not shown in FIG. 3a. FIG. 3b illustrates thelines of force 24 of such a magnetic field.

The voltage commutated by the tube, is determined by the electricstrength of the gap between the electrodes 3 and 4 and may reach 200 400kv. At higher voltages it may prove to be difficult to maintain theelectric strength of this gap, although there is no electron beam wherethis high voltage is applied to the gap. The current in the tube may beincreased by increasing the number of layers in the annularconstruction. Allowance whould be made for the interaction of electronbeams, which affects particularly the trajectory of electrons in the twoextreme beams.

FIGJ4 illustrates another embodiment of the electron tube in 'which thecathode K is designed in the form of a series of plates 25 set parallelto the tube axis 23 along a cylinder generatrix, the first electrode 3is designed in the form of a series of rods 26 parallel to the plates25and interspaced by gaps 27 for the passage of electron beams, theplate 2 is designed in the form of a series of chambers 28 equal innumber to the plates and set along a circumference larger in radius thanthe cylinder generatrix, each chamber 28 being set opposite its plate 25and provided with an annular slot 29 to receive the electron beam.

The second electrode 4 is designed in the form of a series of rods 30equal in number to the chambers placed near the chambers 28 andinterspaced by gaps 31 to match the annular slots 29. It should be notedthat the cross-sections of the gaps 511 are 5 to 50 times as large asthe cross-sections of the gaps 2'? to provide the minimum density of theelectron beam near the plate 2. I

Electric current may be passed through the rods 30 of the electrode 4 inthis embodiment of the tube, to set up a magnetic field, as describedabove.

Thetube in this embodiment operates like the tube illustrated in FIGS.3a, 3b. r

This tube design like the embodiment illustrated in FIGS. 3a, 3b,provides a reduced beam density in the deceleration zone. The range ofcharacteristics in which the tube designs shown in FIGS. 3a, 3b and 4may operate embraces currents of hundreds and thousands of amperes, themaximum operating voltage of 200-400 kv, a voltage drop across the tubein conduction amounting to tens or hundreds of volts. r The tube designsin FIGS. 3a, 3b and a can provide heavier currents and smaller voltagedrops as compared to the embodiment in FIG. 2 but are used for lowercommutated voltages.

What is claimed is:

l. A high voltage electron tube comprising:

a vacuum envelope;

a plate member disposed in said vacuum envelope;

a cathode member disposed in said envelope;

a first electrode to accelerate an electron beam placed in said vacuumenvelope near said cathode member;

second electrode placed in said vacuum envelope between said firstelectrode and said plate member at such a distance from said firstelectrode so as to ensure the electric strength in a gap between saidfirst and second electrode under the conditions when an inverse voltageis applied to the tube, whereas under the conditions when a forwardvoltage is applied to the tube, the potentials of both said electrodesare close to each other and the potential of said plate member issubstantially lower than that of said second electrode and close to thatof said cathode member; and

said plate member being a chamber anode and having a surfacesubstantially larger than an orifice in said second electrode for thereception of a decelerated electron beam.

2. A high voltage electron tube as claimed in claim 1, which includes asystem of magnetic lenses disposed between said first and secondelectrodes for focusing the electron beam.

3. A high voltage electron tube comprising:

a vacuum envelope;

a plate member disposed in said vacuum envelope;

a cathode member disposed in said envelope, said cathode membercomprising a series of concavefaced rings placed one beside the other;

a first electrode to accelerate an electron beam placed in said vacuumenvelope near said cathode member, said first electrode comprising aseries of rings placed one beside the other around said cathode memberand inter-spaced by uninterrupted annular gaps for the passage ofelectron beams;

said plate member comprising a series of annular chambers equal innumber to said cathode rings placed one beside the other and havinguninterrupted annular slots to receive electron beams; and secondelectrode placed in said vacuum envelope between said first electrodeand said plate member for producing an approximately equipotential spacein a gap between said first and second electrodes, said second electrodecomprising a series of rings placed one beside the other near annularchambers of said plate member and inter-spaced by the annular gapscorresponding to said annular slots of annular chambers, thecross-sections of said annular gaps between said second electrode ringsbeing substantially larger than those of said annular gaps between saidfirst electrode rings to ensure a minimal density of the electron beamnear said plate member.

4. A high voltage electron tube comprising:

a vacuum envelope;

a plate member disposed in-said envelope;

a cathode member disposed in said envelope, said cathode membercomprising a series of plate members along the gcneratrix of a cylinder;

a first electrode to accelerate an electron beam placed in said vacuumenvelope near said cathode member, said first electrode comprising aseries of rods equal in number to said plate members placed around saidcathode member parallel to said plate members and inter-spaced by gapsfor the passage of electron beams;

first electrode rods to ensure a minimal density of the electron beamnear said plate member.

5. A high voltage electron tube as claimed in claim 3, wherein saidsecond electrode is provided with a means of setting up a magnetic fieldin its gaps for protection thereof against the electron beam.

6. A high voltage electron tube as claimed in claim 4, wherein saidsecond electrode is provided with a means of setting up a magnetic fieldin its gaps for protection thereof against the electron beam.

I I l 8

1. A high voltage electron tube comprising: a vacuum envelope; a platemember disposed in said vacuum envelope; a cathode member disposed insaid envelope; a first electrode to accelerate an electron beam placedin said vacuum envelope near said cathode member; a second electrodeplaced in said vacuum envelope between said first electrode and saidplate member at such a distance from said first electrode so as toensure the electric strength in a gap between said first and secondelectrode under the conditions when an inverse voltage is applied to thetube, whereas under the conditions when a forward voltage is applied tothe tube, the potentials of both said electrodes are close to each otherand the potential of said plate member is substantially lower than thatof said second electrode and close to that of said cathode member; andsaid plate member being a chamber anode and having a surfacesubstantially larger than an orifice in said second electrode for thereception of a decelerated electron beam.
 2. A high voltage electrontube as claimed in claim 1, which includes a system of magnetic lensesdisposed between said first and second electrodes for focusing theelectron beam.
 3. A high voltage electron tube comprising: a vacuumenvelope; a plate member disposed in said vacuum envelope; a cathodemember disposed in said envelope, said cathode member comprising aseries of concave-faced rings placed one beside the other; a firstelectrode to accelerate an electron beam placed in said vacuum envelopenear said cathode member, said first electrode comprising a series ofrings placed one beside the other around said cathode member andinter-spaced by uninterrupted annular gaps for the passage of electronbeams; said plate member comprising a series of annular chambers equalin number to said cathode rings placed one beside the other and havinguninterrupted annular slots to receive electron beams; and a secondelectrode placed in said vacuum envelope between said first electrodeand said plate member for producing an approximately equipotential spacein a gap between said first and second electrodes, said second electrodecomprising a series of rings placed one beside the other near annularchambers of said plate member and inter-spaced by the annular gapscorresponding to said annular slots of annular chambers, thecross-sections of said annular gaps between said second electrode ringsbeing substantially larger than those of said annular gaps between saidfirst electrode rings to ensure a minImal density of the electron beamnear said plate member.
 4. A high voltage electron tube comprising: avacuum envelope; a plate member disposed in said envelope; a cathodemember disposed in said envelope, said cathode member comprising aseries of plate members along the generatrix of a cylinder; a firstelectrode to accelerate an electron beam placed in said vacuum envelopenear said cathode member, said first electrode comprising a series ofrods equal in number to said plate members placed around said cathodemember parallel to said plate members and inter-spaced by gaps for thepassage of electron beams; said plate member comprising a series ofchambers equal in number to said plate members set around acircumference larger in radius than said cylinder generatrix eachopposite its said cathode plate member and provided with slots toreceive electron beams; and said second electrode comprising a series ofrods equal in number to said chambers placed near said plate chambersand interspaced by gaps to match said chamber slots, the cross-sectionsof said gaps between said second electrode rods being substantiallylarger than those of said gaps between said first electrode rods toensure a minimal density of the electron beam near said plate member. 5.A high voltage electron tube as claimed in claim 3, wherein said secondelectrode is provided with a means of setting up a magnetic field in itsgaps for protection thereof against the electron beam.
 6. A high voltageelectron tube as claimed in claim 4, wherein said second electrode isprovided with a means of setting up a magnetic field in its gaps forprotection thereof against the electron beam.